I. AXIAL REGION
A. Head – most anterior, triangular part w/c is flattened dorso-ventrally 1. Snout – blunt apex of the head
2. Mouth – large anterior opening w/c extends postero-laterally up to the head’s base > dorsal & ventral lip folds – immovable folds that border the mouth dorsally & ventrally – provided w/ valves w/c are associated to respiratory movements – provided w/ valves w/c are associated to respiratory movements 3. External nares or nostril – pair of slit-like openings immediately postero-lateral to snout
4. Eyes – pair of large structures w/c protrude on the dorso-lateral sides of the head and posterior to the nostrils. > Upper Eyelid – thicker structure; borders the eye dorsally; very little movement > Lower Eyelid – thinner structure; borders the eye ventrally; more movable > Third Eyelid or nictitating membrane – thin, transparent, freely movable membrane w/c continuous w/ the inner fold of the lower eyelid.
– homologous to the vestigial PLICA SEMILUNARIS – a fold like structure located near the median corner of the human eye. > Orbit or eye socket – socket where eyes retract
> Cornea – exposed transparent part of the eye
> Conjunctiva – thin transparent membrane w/c is continuous w/ the inner surface of the eyelids. > Conjunctiva – lies and inseparably adheres to the outer surface of the cornea > Pupil – dark, centrally located opening through w/c light can enter the eye > Iris – pigmented, curtain-like structure w/c surrounds the pupil > Iris – regulates the size of the pupil depending upon the intensity of light > Browspot – small, lighter-colored circular spot at about the anterior level of the eye > Tympanic membrane (Tympanum) – smooth, somewhat circular, thin membrane, postero-lateral to the eye. B. Trunk – much bigger part of the body & is situated posterior to the head, having no distinct neck 1. Hump – distinct dorsal elevation about the middle of the trunk; due to...